1. Field of the invention
The present invention is broadly concerned with rye-derived bread improvers which can be incorporated into otherwise conventional wheat flour bread to give improved baked bread having increased loaf volumes and improved crumb quality. More particularly, the invention pertains to bread improvers in the form of one or more water soluble alkaline proteinaceous species derived from rye and having a pI of greater than about 7.5. In preferred forms, the improvers of the invention give at least about a 2% increase in loaf volume and improved crumb grain.
2. Description of the Prior Art
Wheat is a unique cereal which is widely used for the production of bread with good loaf volume and crumb grain. Indeed, when wheat flour is mixed with water and yeast, a dough develops due to the special properties of the wheat storage proteins, i.e., the so-called gluten.
The properties of the gluten network determine the quality of the resulting bread. The right gluten characteristics lead to a well manageable dough with optimum visco-elastic and gas retention properties and, finally, to a bread of high volume and a correct crumb structure. While the quantity and the quality of the gluten proteins are important in breadmaking, the presence of a number of enzymes, lipids and other constituents is also important for the quality of wheat flour for bread-making (Hoseney, 1994).
In areas where wheat is grown, plant breeders have developed wheat varieties that are suitable for breadmaking. Furthermore, cereal chemists around the world have investigated the precise role of cereal constituents in breadmaking and ways to improve several aspects of bread quality, such as bread volume and crumb structure, crumb softness, springiness and staling. Such efforts have resulted in the introduction of a number of enzymes, fats, emulsifiers, oxidants as well as reducing agents and other components in breadmaking recipes
The improving effect of oxidants is well known. Commonly used improvers such as potassium bromate and azodicarbonamide are both strong oxidants. However, potassium chlorate, apparently an even stronger oxidant than potassium bromate, has no effect in breadmaking. Therefore, the evidence that the positive effect found in breadmaking is a mere oxidation is not really definitive. Joergensen (1945) found that ascorbic acid, a strong reducing agent, has an oxidative effect on bread dough. It has been shown that ascorbic acid does not have an oxidizing effect on dough if it is mixed in an atmosphere of nitrogen and, therefore, it is presumed that the ascorbic acid is oxidized by oxygen and that ascorbic acid oxidase is invoked in this process. Another enzyme heretofore described is one that oxidizes sulphydryl compounds to disulfides with dehydroascorbic acid (Belitz and Grosch, 1986; Kuninori and Matsumoto, 1964a). This enzyme is only active with glutathione in the flour (Kuninori and Matsumoto, 1964b). It is clear that if glutathione is added to white flour, the loaf volume is greatly decreased and the loaf looks underoxidized. The effect can be reversed by addition of an oxidant such as potassium iodate (Lai et al., 1989).
In general, it is believed that compounds such as glutathione, cysteine, ascorbic acid, potassium bromate, azodicarbonamide and others have an impact on the ratio between thiol and disulfide moieties in dough, and, hence, on its quality. Furthermore, some scant evidence indicates that, in some instances, enzymes may play an important role in the processes that eventually lead to the bread improving effects.
Thus, while considerable research has been done on various bread additives, the complex chemistry involved is often not fully understood. Moreover, certain types of known chemical bread improvers, and especially potassium bromate, are subject to increasingly stringent governmental regulations. It has been suggested that potassium bromate may in the near future be banned from use in bread doughs. Therefore, there is a need in the art for bread improvers which are derived from naturally occurring sources, and preferably grain sources.